The tool used to measure valve spring tension is a valve spring tester, also called a valve spring pressure gauge. It quantifies the force the spring exerts at different compressions, helping technicians verify seat and open pressures.
In practice, technicians rely on this device to determine how much force the spring applies when the valve is seated and when it is open. Accurate readings help ensure valve control, avoid float at high RPM, and confirm that springs meet the engine’s specifications for performance and longevity.
What tool measures valve spring tension
Engine builders rely on a dedicated device that clamps onto the valve stem or the spring and provides a direct readout of spring tension. The tester compresses the spring to a precise height and displays the force in PSI or Newtons.
Common types you’ll encounter include:
- Manual valve spring testers (spring scales): Simple, handheld devices that apply force and read a scale value as you compress the spring.
- Dial-type valve spring testers: Standalone instruments with a dial gauge that shows tension at a chosen compressed height.
- Digital valve spring testers: Electronic devices that display tension on a digital readout and may log data for multiple valves.
- Valve spring kits with adapters: Sets that include the tester plus different adapters to fit various valve sizes and configurations.
Regardless of type, testers typically report seated pressure and open pressure at a specified height. This data is compared to manufacturer specifications to determine whether springs meet the required tolerances for a given engine configuration.
How to use a valve spring tester
Pro workshop practice follows a standard workflow: prepare the engine for testing, select the correct adapter, securely mount the valve spring tester, set the target compression height, and read the seated and open pressures as you compress. Steps are repeated across all valves to build a complete tolerance profile.
Calibration and safety considerations
Always calibrate the device according to the manufacturer’s instructions and observe standard safety practices. Use appropriate protective equipment and ensure the engine is secured and de-energized before handling valve components.
Note: Always follow the tester’s calibration instructions and the engine’s service manual for the exact pressure specs and measurement heights to ensure accuracy and safety.
Here is a concise set of steps commonly used in the workshop:
- Remove the valve covers and identify the valve springs to be tested, selecting the appropriate adapter for the valve size.
- Install the tester so the valve spring sits correctly in the testing cradle and the valve is held in a neutral position.
- Zero or tare the device if required by the model, ensuring no preload biases the measurement.
- Compress the spring to the seated height and record the seated (closed) pressure.
- Further compress to the specified test height and record the open pressure.
- Repeat for all valves in the cylinder head or engine being tested, noting any variances from spec.
- Compare readings to manufacturer specifications and decide on replacement or adjustment as needed.
By standardizing the test conditions, technicians can ensure consistency across cylinders and gauge the overall health of the valve train. Replacement decisions, such as choosing stiffer or lighter springs, depend on the measured pressures and engine goals.
Summary
Valve spring tension is measured with a dedicated valve spring tester, available in manual, dial, and digital variants. The key readings are seated and open pressures at a defined height, which technicians compare against specifications to ensure valve train reliability and performance. Proper calibration and adherence to manufacturer specs are essential for accuracy and engine longevity.